• Title/Summary/Keyword: Triaxial tests

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Behaviour of Nak-dong River Sand on Cyclic Stress History (낙동강 모래의 반복응력이력에 의한 거동)

  • 김영수;박명렬;김병탁;이상복
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11a
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    • pp.295-302
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    • 2000
  • Earthquakes not only produce additional load on the structures and underlying soil, but also change the strength characteristics of the soil. Therefore, in order to analyze soil structures for stability, the behaviour after earthquake must be considered. In this paper, a series of cyclic triaxial tests and monotonic triaxial tests were carried out to investigate the undrained shear strength and liquefaction strength characteristics of Nak-Dong River sand soils which were subjected to cyclic loading. The sample was consolidated in the first stage and then subjected to stress controlled cyclic loading with 0.1Hz. After the cyclic loading, the cyclic-induced excess pore water pressure was dissipated by opening the drainage valve and the sample was reconsolidated to the initial effective mean principal stress(p/sub c/'). After reconsolidation, the monotonic loading or cyclic loading were applied to the specimen. In the results, the undrained shear strength and liquefaction strength characteristics depended on the pore pressure ratio(Ur=U/p/sub c/'). The volume change following reconsolidation can be a function of cyclic-induced excess pore water pressure and the maximum double amplitude of axial strain.

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Effect of grain size on the shear strength of unsaturated silty soils

  • Onturk, Kurban;Bol, Ertan;Ozocak, Askin;Edil, Tuncer B.
    • Geomechanics and Engineering
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    • v.23 no.4
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    • pp.301-311
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    • 2020
  • In this study, shear strength behavior of fine-grained soils was investigated under unsaturated conditions. The samples in the unsaturated state were subjected to a net normal stress (σ-ua) of 40 kPa and different matric suctions (ua-uw) of 50, 100 and 150 kPa. The matric suction values applied in the triaxial tests were selected according to the bubbling pressures determined from the SWC curves. The study was carried out on prepared re-constituted cylindrical samples by uniaxial consolidation of soil slurries. First, consolidated drained (CD) triaxial compression tests were performed on the saturated samples and the cohesion and angle of internal friction were determined. After that, drained triaxial compression tests under matric suctions were performed on the unsaturated samples. In order to obtain unsaturated test results, cohesion and internal friction angle values of saturated samples were used. The nonlinear surface representing the shear strength surface was approximated consisting of two planes (double planar surface). The reason for the nonlinear behavior of some soils is that the amount of sand content contained in it is relatively high and the bubbling pressure/permanent water content value is relatively low.

Experimental Study on Characteristics of Granular Materials Containing Recycled Aggregates (순환골재를 포함한 입상재료의 특성에 관한 실험적 연구)

  • Hong, Seok-Woo;Gwon, Gi-Cheol;Han, Yeong-Seong
    • International Journal of Highway Engineering
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    • v.15 no.2
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    • pp.83-94
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    • 2013
  • PURPOSES : In Korea, most designs of pavement had been mainly performed by considering CBR of granular materials before KPRP(Korea Pavement Research Program) and 86 AASHTO design method were introduced. Since then, the trend of the pavement designs gradually have moved to using mechanical characteristics throughout the resilient modulus based on the test results up to recently. In this study, we should like to research the mechanical characteristics of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. METHODS : The kinds of materials were tested; coarse grained subbase materials, refining aggregates base materials and recycled aggregates. RESULTS : The present study aims to figure out the resilient modulus of paving materials containing Recycled aggregates through the cyclic loading triaxial compression tests. CONCLUSIONS : The test results revealed that the engineering properties of the recycled aggregates were more excellent than the those of others.

Liquefaction and post-liquefaction behaviour of a soft natural clayey soil

  • Kheirbek-Saoud, Siba;Fleureau, Jean-Marie
    • Geomechanics and Engineering
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    • v.4 no.2
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    • pp.121-134
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    • 2012
  • The paper presents the results of identification, monotonous and cyclic triaxial tests on a potentially liquefiable soil from the Guadeloupe island. The material is a very soft clayey soil whose susceptibility to liquefaction is not clear when referring to index properties such as grain size distribution, plasticity, etc. The classifications found in the literature indicate that the material has rather a "clay-like" behaviour, i.e., is not very susceptible to liquefaction, but its properties are very close to the threshold values given by the authors. Cyclic triaxial tests carried out on the material under different conditions show that liquefaction is possible for a relatively important level of cyclic deviator or number of cycles. The second part of the paper is devoted to the study of the recovery of the soil after liquefaction and possibly reconsolidation. For the specimens tested without reconsolidation, that simulated the soil immediately after an earthquake, the recovery is nearly non-existent but the drop in pore pressure during extension results in a small available strength. On the contrary, after reconsolidation, the increase in strength of the liquefied specimens is quite large, compared to the initial state, but with unchanged failure envelopes.

EVALUATION OF SHEAR BEHAVIOR OF LARGE GRANULAR MATERIALS WITH DIFFERENT PARTICLE SIZES BY TRIAXIAL TEST AND NUMERICAL SIMULATION

  • Kim, Bum-Joo;Sagong, Myung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09c
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    • pp.55-60
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    • 2010
  • Rockfill zones in CFRD consist typically of large granular materials, usually the maximum particle size up to several meters, which makes laboratory testing to determine the mechanical properties of rockfill difficult. Commonly, the design strength of the rockfills is obtained by scaling down the original rockfill materials and performing laboratory strength tests for the reduced size materials. The objective of the present study is to investigate the effect of particle size on the shear behavior and the strength for granular materials. A series of large-scale triaxial tests was conducted on large granular materials with the maximum particle size varying from 20 to 50mm. The test results showed that overall shear behaviors were similar between the samples with different particle sizes while there were slight differences in the magnitudes of the peak shear stress between the samples. In addition, a simulation of the granular material with the max. particle size of 20mm was performed using DEM code, $PFC^{2D}$, and compared with the test results. The deviatoric stress versus strain behaviors of experimental and numerical tests were found to be matched well up to the peak stress state.

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A Basic Study on Borehole Breakout under Room Temperature and High Temperature True Triaxial Compression (상온 및 고온 하 진삼축압축실험을 이용한 시추공의 파괴 거동 기초 연구)

  • Yoon, Jeonghwan;Min, Ki-Bok;Park, Eui-Seob;Jung, Yong-Bok
    • Tunnel and Underground Space
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    • v.30 no.6
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    • pp.559-572
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    • 2020
  • This paper performs laboratory experiments for borehole stability considering temperature and true triaxial stress condition, and observes a thermo-mechanical behavior of the rock under stress and temperature conditions of deep underground. China yellow sandstone and Hwangdeung granite specimens were used to perform a true triaxial compression test. Mechanical tests were carried out under nine confining pressure conditions, and thermo-mechanical tests using granite samples were carried out under six confining pressure conditions at 60-100℃. In the mechanical tests, maximum principal stress at borehole breakout was proportional to intermediate principal stress. In the thermo-mechanical tests, it was confirmed that thermal stress is added to the stress field of the borehole with the increase in temperature, resulting in additional breakout progress. To analyze the results of the laboratory experiment, Mogi-Coulomb failure criterion was used. The results of traditional triaxial compression test on cylindrical specimens and borehole breakout under true triaxial compressions matched well with Mogi-Coulomb failure criterion.

An Experimental Study on Dynamic Deformation Properties of Rock Materials using Large Triaxial Testing Apparatus (대형진동삼축시험기를 이용한 암석재료의 동적변형특성에 관한 실험적 연구)

  • 신동훈
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.299-308
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    • 2003
  • In order to investigate the dynamic deformation properties of rockfill materials in small strain level, cyclic triaxial tests were conducted using the large cyclic triaxial testing apparatus, which was developed by Water Resources Research Institute of KOWACO in 2001. Two types of rockfill materials consisting of granite and shale-sandstone were tested in this study. The test results show that G/G$\_$max/ of granite specimen decreases more than that of shale-sandstone with the increase of shear strain and the increase ratio in the maximum shear modulus G$\_$max/ of granite is bigger than the ratio of shale-sandstone.

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Comparison of Shear Strengths of Crushed Rock Determined by Large Triaxial Test and Direct Shear Test (대형삼축압축시험 및 대형직접전단시험에 의한 사석재료의 전단강도 평가)

  • 신동훈;안태봉;이경필;이한출
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.10a
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    • pp.259-264
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    • 2002
  • In this study the shear strengths of a poorly grad ed rock material(d/sub max/≤50.8mm, C/sub u/=1.86) were determined by large direct shear test and large triaxial test. The obtained stress-strain curves by the above large shear tests for the rock materials are similar to the loose sand's or normally consolidated clay's curve, in which the peak strength does not appear obviously. And for the uniformly graded rock material the shear strength by large direct shear test may be overestimated around 1.54∼1.70 times that of large triaxial test.

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A Study on the Liquefaction Behavior of Bottom Ash (Bottom Ash의 액상화 저항특성 연구)

  • Yoon, Won-Sub;Chae, Young-Su
    • Journal of the Korean Geotechnical Society
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    • v.27 no.6
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    • pp.63-79
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    • 2011
  • In this study relative density tests of bottom ash and standard sand were carried out. And cyclic triaxial tests for samples with the relative density of 40%, 55%, and 70% were carried out on the basis of the test results. Cyclic triaxial tests were also conducted for fines content with 55% relative density. Residual samples were divided into No.40, No.60, No.60, and No.100, and No.200. In order to avoid crashing that can happen when compaction of the sample is initiated, bottom ash was crushed using the a compact mold. In consideration of the crushing characteristics of each residual samples, the fragmentation rate increased up to 30%, which led to the adjustment of fine-grained amount to 10%, 20%, and 30%. Through the repative triaxial test in accordance with the relative density, resistant characteristics of the liquefaction of bottom ash was analyzed. Test results show that, crushing strength of bottom ash was smaller than that of standard sand, resulting in different liquefaction behavior characteristics. And we could find fines content with maximum resistant characteristics of the liquefaction.

Cyclic Liquefaction Behavior Characteristics of Saemangeum Dredged Sand (새만금 준설모래의 동적 액상화 거동 특성)

  • Jeong, Jin-Seob;Choi, Du-Hon;Park, Seung-Hae
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2001.10a
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    • pp.351-354
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    • 2001
  • Undrained cyclic triaxial compression tests were performed on Saemangeum dredged sand to evaluate factors affecting liquefaction strength and liquefaction behaviour characteristics. The results of these tests show that cyclic liquefaction can occur not only very loose sand(Relative density is 30%) but also dense sand(Relative density is 70%). To evaluate effect of the over consolidation ratio on the liquefaction strength, a series of undrained cyclic triaxial compression test was peformed, and the result of this test showed that the liquefaction of this test showed that the liquefaction strength of Saemangeum dredged sand approximately increased to square root of over consolidation ratio in the range of O.C.R value of 1.0 to 4.0. In the anisotropically consolidated sample tests, the liquefaction strength is increased by increasing the effective consolidation ratio.

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